funnel and the filter being washed with ether ; the ether is distilled off on
a water-bath, the greater part of it being condensed. If any drops of water
remain in the flask, they are eliminated by heating on a boiling water-bath
after addition of a few c.c. of alcohol. The flask is again weighed when
cold, the increase representing the fatty acids and resins present either free
or combined as soaps, plus the neutral fats and non-saponifiable oils ; the
percentage of such substance may be denoted by a. The acid number is
then determined on the whole ethereal extract in the flask itself ; multipli-
cation of the acid number by — gives the percentage (b] of fatty (or resin)
acids found in the free state or as soaps. If from this is subtracted the
amount of free acid—calculated with the same coefficient—found as under
4 (above), the remainder represents the acids of the soap ; the amount of
soap is then calculated in accordance with the nature of the base it contains.
6. Detection and Determination of Neutral Animal and Vegetable
Oils and Fats.—The liquid remaining in the flask after the determination of
the acidity is heated -on the water-bath for about an hour with excess of
alcoholic potash and the excess of the latter then titrated ; this gives the
saponification number of the neutral fats present. Multiplication of this
number by — gives the percentage (c) of neutral fat.
7. Investigation of the Unsaponifiable Matter.—The amount of
this may be ascertained from the values already obtained (5 and 6), since it
equals a— (b + c).
When, however, it is necessary to separate and examine it, the pro-
cedure varies according as resins or resin soaps are present or absent.
In the latter case, about 50 grams of the lubricant are shaken vigorously
with at least 200 c.c. of ether in a separating funnel until the oils are dis-
solved. A kind of emulsion holding the soaps in suspension is thus formed
and filtration of this through a large pleated filter gives a clear ethereal
solution containing, besides mineral oils, resin oils and tar oils, also any
fats present. The ether is distilled off—the last traces being evaporated
over a boiling water-bath—and the saponification number determined on
a part of the residue. If there is any saponification number, fats are present;
in such case, the non-saponifiable oils are separated by saponification in
the cold (see Heavy Oils, Chemical Tests, 5), and the mineral, resin and
tar oils investigated by the methods indicated for heavy mineral oils.
When, however, resins or resin soaps are present, to separate the non-
saponifiable oils, the substance is extracted with acid ether (see 5, above),
the ether evaporated, the residue washed with 90% alcohol to dissolve
the resin, the insoluble residue saponified in the cold (see Heavy Oils,
Chemical Tests, 5) and the mineral, resin and tar oils investigated as
with heavy mineral oils.
When the lubricant contains wool fat, a non-saponifiable residue is obtained
which may be confused with mineral oils, but may be distinguished by deter-
mining the rotatory power and the iodine number of the residue itself. With,
mineral oils the specific rotation is usually not more than [a]^ = 3 and the iodine
number usually below 6 and only rarely above 14. With wool fat, the unsaponi-maining turbid ; with artificial vaselines, a flocculent